This invention relates to combustion engines and more particularly to electrically controlled intermittently operative injection arrangements having at least one injection means which is operated synchronously with the cam shaft rotations and which furnishes a quantity of fuel during each operating cycle of the machine which depends upon the pressure or volume of air in the intake means following the throttle valve in the direction of air flow through said air intake means. Generally, the injection valve is kept open for a period of time depending on said air pressure or volume, the fuel being furnished at a constant pressure. Further, in combustion engines of the type under discussion, there is an arrangement for controlling the engine during free running conditions.
In known fuel injection arrangements, when the engine is in a free running position, that is when the engine speed is substantially above the idling speed even in the presence of a closed throttle valve, a disconnecting arrangement is provided which either prevents the generation of electrical opening pulses for the injection means or else prevents said electrical opening pulses from reaching a power amplifier state immediately preceeding the solenoid valves which perform the injection. In these known systems, injection is prevented until the engine speed is no longer above the idling speed by a predetermined margin. Since no fuel is injected, of course, no harmful exhaust gases can be emitted. However, it has been found to be very disadvantageous that the exhaust system undergoes a very substantial cooling during this period. Thus, not only can a considerable power loss occur in any subsequent acceleration process, but also a great increase in the number of harmful gases emitted by the engine can occur.